A heterogeneous network includes segments that are subject to varying distribution parameters such as bandwidth, latency, and jitter, as well as protocol and routing restrictions. Such parameters establish the level of performance of each network segment, commonly referred to as me “quality of service” (QoS). Heterogeneity of a network can create deficiencies in the broadcast quality of information simultaneously transmitted to disparate locations on the network, especially when contradictory network policies and QoS mechanisms are imposed. To achieve real-time distribution of multimedia over a heterogeneous network, the data must adapted so as to reach all intended recipients simultaneously, or in other words, such that the data is not delayed by any limitations imposed by the topology of the network. For example, simultaneous compression of the data may be required to compensate for low bandwidth of a particular network segment. However, compressing data on the fly can lead to unacceptable latency. Potential measures which address this latency include the utilization of special hardware or low efficiency compression algorithms, sacrificing resolution, reducing the frame size, or reducing the number of frames per second.
One approach to distributing content over a heterogeneous network is to format and to transmit multimedia content separately to each segment according to its QoS parameters. This approach is disadvantageous in that the bandwidth required to achieve simultaneous distribution increases according to the number of segments that have a different QoS. Another approach is to minimize the number of simultaneous transmissions by supporting a limited number of QoS levels, including a best-effort class. This approach is suggested in an article by Salgarelli et al, entitled “Supporting IP Multicast Integrated Services in ATM Networks” Proceedings of SPIE Voice & Video '97, Broadband Networking Technologies. Such an approach reduces the additional bandwidth consumed although at the expense of optimizing performance.
Each network segment may be subject to a different limitation, so the compensating measures that are appropriate for one segment are not necessary for another. The approaches discussed above require either a single scheme that compensates for the limitations of the network as a whole, or multiple simultaneous transmissions involving different compensations schemes. What is needed is a system of distributing multimedia content from a single source to multiple recipients located at various points in a heterogeneous network, that maximizes the capabilities of each recipient segment while minimizing the resources consumed at any one point on the network.
This invention addresses the needs described above by providing systems and methods of distributing multimedia content over a heterogeneous network. The systems and methods of this invention optimize the distribution of multimedia content from a central source to multiple destinations along a heterogeneous network by transmitting multimedia content more efficiently, reliably and consistently, regardless of the distribution parameters of various segments of the network (e.g., unicast, or multicast).
More specifically, this invention permits a distribution of multimedia to be adapted locally to conform to the parameters imposed by each recipient network segment, m other words, rather than adapt the content at the source, the content is adapted by dispersed media servers that are located between the network backbone each recipient network segment. Accordingly, multimedia can be distributed along a network backbone such that the single distribution of multimedia can take full advantage of the capabilities of the network by being adapted to conform to network segments having the least restrictive limitations as well as to network segments having the most restrictive limitations. When the stream reaches a dispersed media server, that media server adapts the stream according to the topology of each segment that is downstream from that media server, and upstream from a segment endpoint (typically a recipient or other media server).
According to an exemplary embodiment of the invention, each media server is programmed to adapt data according to the distribution parameters of each network segment that is adjacent to and downstream from that media server. The system then transmits multimedia content from a central source to the programmed media server, which adapts the transmission, thereby yielding for example an advantageous reduction of the bandwidth consumed at the source upon transmission of the multimedia content. After a media server adapts the data, the media server transmits the data to any targeted recipients and media servers along the adjacent network segment or segments. Thus, the systems and methods optimize the distribution of multimedia content based upon the quality of service (QoS) parameters of targeted segments of a network at a given time. If segment parameters change, the dispersed media servers are reprogrammed to adapt to accommodate the new network parameters.
A second or subsequent dispersed media server may be located on a secondary or subsequent network segment downstream from a first dispersed media server that is located between the network backbone and a primary network segment. In other words, network segments may branch off to more network sub-segments. Each second or subsequent dispersed media server receives data that has been adapted by the preceding dispersed media server, and further adapts the data to conform to the parameters associated with the adjacent and downstream network segment or segments.
Other advantages and features of the invention will be apparent from the description below, and from the accompanying papers forming this application.